When Vernon Sharpe is picked up by the pickup truck driver (around 30:27), we see the same farm that is across the street from his gas station. The guardsman left behind by Colonel O'Neill, to see if Sharpe comes back, would've been able to observe Vernon standing in front of his gas station driveway when he got picked up.
During the airport scene, which is supposed to be in Colorado, all of the planes have Canadian registrations.
When Jonas and Sam are investigating the device, you can see the light bulbs inside it.
Since the ability to see the bleed-through creatures from the other dimension is transferred from person to person by touch, Dr. Fraiser should have been the 2nd person to see those creatures. She had to touch Jonas to do the various testing on him which was before anyone else had started seeing the creatures.